If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Re: Using Li-ion cells in LED flashlights safely

I think I just learned something from this post I did not realize. I had assumed if you placed 2 cells in series you got twice the voltage and the same amount of mAh. But it appears that the regulator in the light will change that, so you end up with more potential mah than I originally thought.

Does that mean if you have a light like the Spark SD52 that uses 2XAA cells but with their regulated circuit accepting up to 7.6v, you could use the 3.2v LiFePO4 AA cells and get a lot more output?

BTW, as a follow up on your post I contacted K2Energy to see about getting their cells in Canada. There are no K2Energy dealers in Canada. For now it will be a deal breaker for most Canadians. The reason for that is due to USPS regulations US Dealers cannot ship Li Ion via USPS. The alternative, getting small orders via UPS and Fedex from the USA is a nightmare that most Canadians now avoid, so it will not work. However Canadian Postal regulation 3.2.2.8 allows for Li Ion cells if they follow certain prescribed protocols as set out in the prevailing Shipment of Dangerous Goods Act, and EMS seems to dovetail into that so Hong Kong/Chinese eBay sellers are successfully selling LiFePO4 into Canada, so it will boil down to finding some other reputable source there rather than in the USA I'm afraid.

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by TSellers

I think I just learned something from this post I did not realize. I had assumed if you placed 2 cells in series you got twice the voltage and the same amount of mAh. But it appears that the regulator in the light will change that, so you end up with more potential mah than I originally thought.

Does that mean if you have a light like the Spark SD52 that uses 2XAA cells but with their regulated circuit accepting up to 7.6v, you could use the 3.2v LiFePO4 AA cells and get a lot more output?

BTW, as a follow up on your post I contacted K2Energy to see about getting their cells in Canada. There are no K2Energy dealers in Canada. For now it will be a deal breaker for most Canadians. The reason for that is due to USPS regulations US Dealers cannot ship Li Ion via USPS. The alternative, getting small orders via UPS and Fedex from the USA is a nightmare that most Canadians now avoid, so it will not work. However Canadian Postal regulation 3.2.2.8 allows for Li Ion cells if they follow certain prescribed protocols as set out in the prevailing Shipment of Dangerous Goods Act, and EMS seems to dovetail into that so Hong Kong/Chinese eBay sellers are successfully selling LiFePO4 into Canada, so it will boil down to finding some other reputable source there rather than in the USA I'm afraid.

Actually the mah's remains the same. The switch mode regulator converts high voltage low current to lower voltage higher current. As the batteries drain & the voltage goes down the regulator increases the current draw in order to maintain performance. Inserting a higher voltage battery does not really noticeably increase the performance of the light. As you increase voltage you increase runtime for a given mah rating & brightness. you do not actually increase the mah rating or noticeably increase brightness with the extra voltage. This extra current draw as the battery drains serves to kill the battery faster though so most manufacturers allow their lights to go out of regulation eventually once a certain voltage level is reached. This serves to extend the usable life of non rechargeable batteries as opposed to maintaining tight regulation till drained & serves to be a warning to replace rechargeable batteries as by this time they are drained & running them longer could damage them to the point of not being able to recharge them in some cases.

Re: Using Li-ion cells in LED flashlights safely

Ok I am curious then... How about those Li-ion batteries that are in smartphones and cell phones and digital cameras etc? Same rules apply? Don't overcharge, don't discharge too fast, and do not leave them unattended? If this is the case, there are a whole world of people out there who are charging their batteries wrong. I am curious to know if these flashlight type rechargables are different in any way from those in typical consumer products? I am planning on buying some flashlights which require a 18650 battery, but after reading here, I am actually skeptical to do so. I can't just wait around while my batteries charge up, have no idea what is the ideal charge time for slow charging either. I leave my mobile phone charging all night, sometimes the camera batteries charge all night too, many times while I am away. So far I have been lucky I guess? I may stop doing this now after reading the first post.

Do not chargable CR123's pose any risk in flashligts if not used for long periods of time?? Or is this terroist cell issue only for rechargable batteries? I so wish Eneloops would come out with both a CR123 and an 18650, I would feel somewhat better.

Re: Using Li-ion cells in LED flashlights safely

Your smartphones, cell phones and digital cameras all have dedicated chargers and protection circuits all over the place. The chargers and protection ensure they don't charge too fast and they don't overcharge. The protection in the device ensures they don't over discharge. If you have a good charger, protected cells, low voltage warnings in your dropin, then li-ions in flashlights are safe.

Lithium primary CR123A cells don't leak. Care should be taken when using more than 2 cells in a light. Take care that the cells are balanced - have the same or close voltage. One fresh cell and one depleted cell is a recipe for disaster. Never try to recharge lithium primary cells.

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by yoyoman

Your smartphones, cell phones and digital cameras all have dedicated chargers and protection circuits all over the place. The chargers and protection ensure they don't charge too fast and they don't overcharge. The protection in the device ensures they don't over discharge. If you have a good charger, protected cells, low voltage warnings in your dropin, then li-ions in flashlights are safe.

Lithium primary CR123A cells don't leak. Care should be taken when using more than 2 cells in a light. Take care that the cells are balanced - have the same or close voltage. One fresh cell and one depleted cell is a recipe for disaster. Never try to recharge lithium primary cells.

Normally I would plug the phone in directly to the wall through the USB cable, but I think the phone itself has all kinds of protective circuits. Though I do know some phone batteries have also exploded. Other than the charges that were recommend at the beginning post, are their other brands or charges that others would recommend? I am looking for a very good charger, that last thing I need is a bomb. Of course the primary cells are like Alkaline batteries in a way, they cannot and should not be recharged.

For the CR123s basically then when I take them out of the packages from the store, if I am using two in one in a flashlight, I should put a volt meter to them to make srue I find two that are of equal or close voltage? I assume the same care should be taken with a flashlight that needs 2 18650s? If I am only using one in a flashlight there is much less risk correct?

I will have to check if the flashlights I am about to buy have that low warning light. That is Nitecore SRT 5 and 7. I think they do, but I need to check. I know the EA or EC series does.

How long can the 18650's hold their charge before they HAVE to be removed from the flashlight? Or depleted cells are ok to recharge? Or is that the problem? If a depleted cell is charged it may also explode when trying to be recharged?

Re: Using Li-ion cells in LED flashlights safely

HKJ does excellent reviews of cells and chargers. The Xtar VP1 is a recently released unit that gets good reviews. It is flexible and you can select different charging rates to match the requirements of the cell (mainly size or capacity).

Some very good lights/dropins don't have low voltage warnings. They provide regulated output for a range of voltage and "drop out" of regulated and go direct drive. In use, you'll notice the dimming and know to switch cells. In some ways, these designs are based on lithium primary cells, which can be sucked dry.

The key is to have a volt meter to be informed. What was the voltage of the cell before charging, after charging, after a good, long walk, etc. Check the voltage of the cell before going camping. Etc.

Li-ions hold their charge (more or less). Some flashlights, particularly with electronic switches, have a parasitic drain. But this is generally very low and not an issue if you use your light regularly.

Li-ions don't have memory which means it is fine (even good) to top them off when the voltage gets down to 3.8 or even 3.9. Some chargers won't kick in unless the v is below 3.9. There is no need to wait for the protection circuit on the cell to cut off power. You can top off the cell well before the cut off will trigger.

I use a simple volt meter from cottonpicker's in the market place. Great for li-ions, but not for other types of cells.

A good charger will recognize cells that have been overdischarged. They either won't charge the cell or will start on a very low charge input.

Another reference, in addition to the threads on this forum, is Battery University. When used properly and with awareness, li-ions are great.

Re: Using Li-ion cells in LED flashlights safely

I am getting a modded light wich takes over 5A per cell. I am getting the 20R cells (unprotected) for that. So the 2000 mAh cells are discharged with more than 2C, which is described to be dangerous in this guide. Is this still up to date? Or is it OK for such cells?

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by Psychonaut

I am getting a modded light wich takes over 5A per cell. I am getting the 20R cells (unprotected) for that. So the 2000 mAh cells are discharged with more than 2C, which is described to be dangerous in this guide. Is this still up to date? Or is it OK for such cells?

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by germanium

Originally Posted by TSellers

I had assumed if you placed 2 cells in series you got twice the voltage and the same amount of mAh. But it appears that the regulator in the light will change that, so you end up with more potential mah than I originally thought.

Actually the mah's remains the same.

germanium is correct, the mAh's stay the same. But at 2x the voltage, the same mAh's give you 2x the amount of energy (in Watt-hours). Which is logical if you're using 2x as many cells.

If there's a switching regulator in the light (as will be the case for a modern, efficient LED flashlight), the same power draw @ 2x the voltage means 0.5x the current (mA's). At the same mAh rating, that gives you 2x the runtime. Which again is logical if you're using 2 cells vs. 1.

So far the theory! In practice, the mAh's you can get out of a cell, depends on the current draw. At 0.5x some current draw, a cell will likely show higher mAh capacity than at 1x that current draw. Depending on current draw and cells used, the difference may be small, or it may be big. And then you should know that voltage conversion circuitry usually operates (somewhat) more efficiently at higher voltages.

Summarized: putting multiple cells in series may help in more ways than one. But how much, might not be noticeable (apart from the obvious doubling of runtime you could expect). On the flip side: there's some issues with a multi-cell setup (for example, dangers of mixing cells in various state of charge) that you don't have with a single-cell powered light.

Re: Using Li-ion cells in LED flashlights safely

Re: Using Li-ion cells in LED flashlights safely

From personal experience: at least the Chinese-made ones sometimes do.

Probably is Brand dependant. I've been using GP Brand for years and so far not noticed any problem, (do my best not to leave depleted cells in the devices that they were in). Now going to try some other CHinese Brands, just got some Nitecore and some cheap 'WF' brand to try. If any leak it will probably be the latter, and I won't be surprised if their capacity is a lot less than the other two brands mentioned here.

Re: Using Li-ion cells in LED flashlights safely

Great writeup! I just got my first flashlight that takes Li-ion, so this was good information. I'm still looking up information on unprotected 10440's (i just shocked myself, somehow, by removing the safety from it), and am trying to learn as much as i can about the safety of them.

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by MFMIYP

Is there anything to be aware of with stacking protected rechargeable Li-ion's into a light? I recall reading somewhere that it was a must-not.

This is done by a lot of people around here including me, so it's certainly not a "must-not" to everyone. Nevertheless protection circuits are not perfect (some don't work at all) so you should still make sure that any series-wired Lithium-Ion cells are properly balanced. This means that the cells are same type and age, have been tested to have similar capacity, and are starting at the same voltage every time.

Re: Using Li-ion cells in LED flashlights safely

So there are two types of these rechargeable Li-ion batteries: protected, and unprotected, correct?

Some lights using multiple batteries stack in series (meaning one goes in the body/tube, and than another right behind it till full), and some use battery magazines; which I don't yet know if those are actually wired parallel or series, but in any case taking for example the Olight M3X, that's a series stacking light, and so my question going out now is does anyone stack non-protected batteries as a result of my initial question? Further, what more can be said about the concerns of stacking protected batteries in the first place? Or un-protected batteries for that matter?

I get you Disciple, and I'm willing and able to invest in everything it takes to pay close attention to the status of my batteries, and definitely appreciate your input very much. For whatever reason, a windfall of lights is coming to me as a result of my impulsiveness. Of course now there's no turning back, and I do enjoy the details of things which is what brought me here.

So thanks. Lastly what's with the "Image Verification" ...is that all the time??? yikes.

Re: Using Li-ion cells in LED flashlights safely

Disclaimer: I am not a battery expert. I an regurgitating what I have learned here.

Battery magazines (or carriers) can be either series or parallel, or a combination (2s2p). I would not use unprotected cells in a series-wired configuration. If you are sure that all cells are wired in parallel then it should be reasonably safe to use unprotected cells (still of the same type) as they will inherently balance. See Li-Ion Parallel Charging for testing and explanation. However it may still be possible to over-discharge the cells depending on the circuitry of the light, and this can be dangerous as it may damage the cells in a way that can later cause an internal short (read: "vent with flame" which means explosion in a sealed light). If you choose to use unprotected cells (either a single cell or in parallel) make sure the light has a low-voltage cutoff or inherently shuts off before the cells are over-discharged. The forward bias voltage of the LED often serves this purpose. See HKJ's battery selection guide for more. In any light an unprotected cell is at greater risk from an external short or from over-charging from a malfunctioning charger, therefore the protection circuit adds an extra layer of safety in any application.

Series-wired cells are more dangerous because one cell can drive another (depleted) cell into reversal causing a breakdown of the internals of the cell and smoke/fire/explosion/etc. This is why we must check that the cells are properly balanced.

Since charge state can be inferred from voltage in Lithium-Ion cells we can use voltage checks to check capacity. When you charge a set of sells for series application check the voltage after letting them rest for a few minutes. The voltage should be nearly the same. (+/- 0.02v I believe I read? I'm not sure; research this yourself.). A low voltage could be the sign of a degraded cell. When you first use the cells (in series) periodically stop, open the light, and check individual cell voltage, again after a few minutes of rest. The cell voltages should drop at the same rate; one dropping faster than another is a sign of a cell with diminished capacity, and if severe it could result in that cell being depleted early and driven into reversal.

By "Image Verification" do you mean a form of CAPTCHA? If so that must be because you are a new member because I don't see those.

Re: Using Li-ion cells in LED flashlights safely

Thank you, Disciple. A lot of information to consider. I appreciate your reply very much. The CAPTCHA thing is gone too. What about below-freezing temps with these batteries. As far as plain storage, loading them with actual use, or charging while too cold? Seems like I hear the primary type 123 are good to go in basically all temps. I'm concerned about damaging my rechargeable ones. Thanks again.

Re: Using Li-ion cells in LED flashlights safely

Originally Posted by MFMIYP

What about below-freezing temps with these batteries. As far as plain storage, loading them with actual use, or charging while too cold?

Storing them cold is fine, and if they will work, using them cold is fine too - their performance will be lower in extreme cold, but they will warm up in use, and there is no safety issue there I am aware of. But DO NOT charge a frozen battery - that can definitely lead to problems.

From Battery University:"Many battery users are unaware that consumer-grade lithium-ion batteries cannot be charged below 0°C (32°F). Although the pack appears to be charging normally, plating of metallic lithium can occur on the anode during a subfreezing charge. The plating is permanent and cannot be removed with cycling. Batteries with lithium plating are known to be more vulnerable to failure if exposed to vibration or other stressful conditions."

So to repeat, DO NOT charge any lithium ion cell that is below freezing. Storing or using them cold is fine.

Re: Using Li-ion cells in LED flashlights safely

So to repeat, DO NOT charge any lithium ion cell that is below freezing. Storing or using them cold is fine

Thanks for the reminder. I often place the batteries from the headlamps I've been using for a night ski straight into the charger as soon as I come in the door so I won't forget. In fact I did that tonight. Although they are usually coming in from a warm car ride, it's well worth it for me to always be aware of that.

Re: Using Li-ion cells in LED flashlights safely

Quick question...
According to this thread and another one about circuit protection - the protection is there just in case, it shouldn't be relied upon and it shouldn't enter into any "estimations" (e.g. "my cell is protected, so I can torture it"), right? OK. But what is the reasonably safe voltage limit that I should "train" myself not to cross? It says that 3.0V is the absolute minimum for discharging, but if I'm outside, using my torch - at what voltage should I stop using my TF 18650-protected? I wanted to test how much can I use my torch so I turned it on and stopped it as soon as the voltage turned 3.6V. The whole process took 3.5h so I assumed that's the reasonably safe time I can use it. True or not? Can I squize-in some more time or it's pushing it with negligible benefits?

Re: Using Li-ion cells in LED flashlights safely

Thanks for the information. More than 3,5 years late to say it but this is still valuable and actual.

Originally Posted by JBorneu

Don’t discharge until the protection circuit kicks in

So much one needs to know when it comes to batteries, and I am still learning more. Do I understand this right that I therefore never should use Li-ion batteries in regulated flashlights who lacks over discharge protection suited for the voltage of the used Li-ion(s)?

What I have read the overdischarge protection of a 3,7V Li-ion kicks in at 2,5V.

If I then use 2x18500 or 18650 to run, for example, a Malkoff M61SHO dropin, Information from the site: "The input voltage is 5.5- 12 volts. Below 5.5 volts it will drop out of regulation. Below 5 volts it will begin to flash and below 4.5 volts it will shut off. "

This dropin consequently doesn't work at all with a single cell. But with two cells it means that it drops out of regulation when the voltage of each cell is 2,75V. And because this dropin is intended for two Li-ions I presume it's ok to run the light until it drops out of regulation, though the voltage is just slightly over the cells protection limit.

But how to do with a Malkoff M61: "The input voltage is 3.4 - 9 volts. Below 3.4 volts it will drop out of regulation and run direct drive."
Consequently it should be considered as "forbidden" to run this dropin at all with two Li-ions: the light will be flat regulated until the protection circuit kicks in and because there is no warning for when this will occur; is that a correct conclusion ?

Re: Using Li-ion cells in LED flashlights safely

One thing I like to do with NiMH is an occasional runtime test. This way, I know how long my light will run if I use it for long stretches. It also gives me an idea of the health of my batteries. Similar testing, along with voltage readings at regular intervals, might not be a bad idea with Li-Ion. If you know about how long your batteries will run a light before voltage drops below a certain level, you are less likely to overdischarge them. And since most Li-Ion chemistries generally experience gradually decreasing capacity over their lifetime (unlike NiMH), doing runtime tests at regular intervals will let you know how long you can use your light as the batteries age.

Re: Using Li-ion cells in LED flashlights safely

Do I understand this right that I therefore never should use Li-ion batteries in regulated flashlights who lacks over discharge protection suited for the voltage of the used Li-ion(s)?

I would use a protected cell in a light that does not have a driver with a shutoff algorithm. (Actually I would never use a light that does not have a protection circuit built in).

What I have read the overdischarge protection of a 3,7V Li-ion kicks in at 2,5V.

You mean that's where a protection circuit kick's in? I think most are higher than that are they not? I thought 2.5 was the level cited by Battery University as the lowest level a Li-Ion cell can by taken to for up to a week.

I presume it's ok to run the light until it drops out of regulation,

2 cells in series your problem is not the low voltage cutoff, if they were unprotected cells then your concern is with internal resistance causing one of the cells to reverse polarity and vent. Thus you need to use balanced or protected cells in that configuration.

But how to do with a Malkoff M61: "The input voltage is 3.4 - 9 volts. Below 3.4 volts it will drop out of regulation and run direct drive." Consequently it should be considered as "forbidden" to run this dropin at all with two Li-ions:

Can't really understand your question here. Above you mention that the drop-in needs 5.5-12V, then this appears to state the same drop in uses 3.4-9 V, or am I getting it wrong?

I feel comfortable using unprotected cells in my single cell Spark headlamps for example because they have good protection built into them already for low voltage, overvoltage, and reverse polarity. If I were running any 2 cells lights in series I'd use protected cells due to the potential issues with internal resistance from unbalanced cells causing problems with one of the cells.

These opinions are just what my understanding of general guidelines for Li-Ion are from reading the comments of others in the fourms that have more experience than me (that's why I waited 3 days before replying), and from the Battery Universitie's website, so of course you should double check anything I've said before potentially acting on it as good advice.

Re: Using Li-ion cells in LED flashlights safely

Can't really understand your question here. Above you mention that the drop-in needs 5.5-12V, then this appears to state the same drop in uses 3.4-9 V, or am I getting it wrong?

Sorry, expressed me a bit unclear. I compared between the standard M61 which is regulated between 3,4 and 9V and the slightly higher output M61SHO which is regulated between 5,5 and 12V. However I think the standard M61 actually drops out of regulation at slightly higher voltage than 3,4V: with several of my different M61 dropins the brightness is lower with a single 17670/18650 than 2xCR123 or becomes lower after a short while.

I only have high quality Li-ions and only use the same brand and model in pairs. Once I have started to use a pair I mark them and let them continue together. The charger is Pila IBC. I don't know how much they differ from each other. The same brand and model of the higher grade batteries should differ only very slightly I think?

Re: Using Li-ion cells in LED flashlights safely

The same brand and model of the higher grade batteries should differ only very slightly I think?

Well I'm actually running some unprotected cells in a Fenix TK76 in series. They are matched and I monitor and measure them each time they are charged in the same fashion as you. I do not use that light very much as it was given to us for evaluation, but in the long run I accept that I should be using protected cells in it, but at the moment, and given how rarely I use the light, I cannot afford to dedicate 4 expensive protected cells to it. I guess if I was going out on a field operation that I knew would be causing the light to get constant use I would simply swap the cells out for protected ones at that point. Ironically the place I really need to use 14500 protected cells the most is in AA cell packs for VHF radios, but those packs simply do not have the room, always seems to be the problem with protected cells in places you need them the most.